Whether you're driving in a car, walking down the street, or merely sitting in a chair, there are about a hundred ways that life could end: instantly, slowly, ironically, stupidly, early, or even painfully. Yet despite the precariousness native to existence, most of us manage to soldier on.

Every so often, however, we get hung up on something, and our stoic composure gets tossed out the window. Topics like nuclear power, genetically-modified foods, and, more recently, horse meat in food, bring out humanity's true nature, "guided by emotion rather than by reason, easily swayed by trivial details, and inadequately sensitive to differences between low and negligibly low probabilities," as psychologist Daniel Kahneman wrote. In short, we humans are flighty, irrational creatures.

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In 1987, psychologist and risk perception expert Paul Slovic skillfully summarized in the journal Science how we calculate risk. In general, humans tend to be wary and apprehensive of risks that are uncontrollable, potentially fatal, possibly catastrophic, and relatively unknown. A quarter century ago, Slovic described these criteria in the context of nuclear power, and with them in mind, he predicted that genetic engineering would become controversial and frightening to the public. Slovic was certainly prophetic, particularly evidenced by today's contentious debate surrounding genetically-modified food.

Human emotions were road tested in the Stone Age. Yesterday's risks prepare us to fear snakes, lizards, and spiders, although all three combined now kill only a dozen Americans a year. Flying may be far safer than biking, but our biological past predisposes us to fear confinement and heights, and therefore flying.

The fear that Myers describes is founded in emotion, not based in evidence. With this type of fear, misappropriation of risk follows. This is predominantly fueled by what is called the availability heuristic, the human tendency to judge an event based upon the information and examples that are most easily recalled. These days, most fodder for the availability heuristic originates from the Internet or television, where sensationalism and scaremongering are rampant. As we view vivid, frightening images and read disturbing reports, our brain commits them to easily-retrieved memory.

When the availability heuristic runs amok, it can form a self-sustaining "availability cascade," in which—for example—a media story gains such prominence that it reaches the forefront of society's collective memory. When this happens, panic over a fairly minor risk can become rapidly widespread, potentially leading to large-scale government action.

Perhaps the most common modern cause of the availability cascade is terrorism. In the last decade, you'd be hard-pressed to go one day without hearing about it. However, as Reason's Ronald Bailey wrote in 2011, an American's chances of being killed by a terrorist are approximately one in 20 million. Heck, even if all of the thwarted terrorist attacks over the last 10 years were carried out, that still would translate to a risk of one in 1.7 million. Compare that to an infinitely more dangerous activity you may undertake every morning: climbing into a car. The annual risk of dying in a motor vehicle crash is one in 19,000.

Yet despite its benign statistics, we still fear terrorism. That's because it fits right in with Slovic's summary of how we determine risk. Terrorism is uncontrollable (Who knows where terrorists will strike?), fatal (self-evidential), potentially catastrophic (What if they get hold of chemical weapons?), and unknown (Anyone could be a terrorist!).

Since 9/11, the United States has spent well over $1 trillion on anti-terrorism security measures, allowed mass wire-tapping, and turned a trip to the airport into a circus. Did terrorism's false risks merit such high costs?

As skittish primates, we tend to fear, and perceive as risky, the wrong things. But as conscious beings capable of rational thought, we have the ability to recognize those misplaced fears and counteract them. We would all do well to keep this in mind the next time something scary rears it's frightening—or maybe not so frightening—head.

After studying four decades of terrorism, Aaron Clauset thinks he's found mathematical patterns that can help governments prevent and prepare for major terror attacks. The U.S. government seems to agree.